A positively charged particle is held at the center of a spherical shell. The figure gives the magnitude E of the electric field versus radial distance r. The scale of the vertical axis is set by Es = 12.0 x 10' N/C. Approximately, what is the net charge on the shell? Assume r's = 2 cm. E (10' N/C) 0 3T's 4T'S 5T'S r (cm) Number Units